Sunday, December 27, 2009

I have a specific chemistry question. I have been tasked with removing a coffee stain from denim. I used 100% cotton denim and Dunkin' Donuts...

Please understand that food and beverage products like coffee contain hundreds if not thousands of different individual chemicals in varying proportions so trying to develop a strategy based on a single chemical structure is really oversimplifying the situation.  Having said that, you've made some great observations with real logical thinking.  Cotton fibers and colored organic chemicals have a natural adhesion to each other, thus making stain removal difficult.  Oxidation is a good idea here since oxidizing different atoms in these coffee chemicals will disrupt their color properties and essentially make them become colorless.  This is why bleach is such a popular stain removing agent since it is a strong oxidizer.  But chlorine bleach will remove the denim color as well so an oxygen based bleach should be used here.  If we are talking about removing an acidic compound, then actually using a base would be best since it will neutralize the acid and possibly make the compound more water soluble.  As to your last point about polar groups, water is actually a highly polar solvent so if any of the components of the stain are naturally very soluble in polar solvent they will readily dissolve in the water.

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